1. Field of the Invention
This invention relates to methods and apparatus for calibrating solid-imaging devices.
2. Technical Background
Solid-imaging devices have been used for rapid prototyping for models for product development, and, more recently for manufacturing operations. Solid-imaging devices produce three-dimensional objects from fusible powders or photocurable liquids, typically by exposure to radiation in response to computer control. Data representing cross-sectional layers of a three-dimensional object provide the computer with control parameters for programs for automated building of the object, typically layer-by-layer. A laser or other source of actinic radiation suitable for solid imaging sequentially irradiates individual thin layers of the build material in response to which the material transforms layer-upon-layer into a solid, to create a solid imaging product. Example stereolithography apparatus is describe in U.S. Pat. Nos. 4,575,330 and 5,495,328, which patents are incorporated by reference herein.
Solid imaging is sometimes referred to as “rapid prototyping and manufacturing” and includes such diverse techniques as stereolithography, laser sintering, ink jet printing, and others. Powders, liquids, jettable phase-change materials, and other materials for solid imaging are sometimes referred to as “build materials.” The three-dimensional objects that solid imaging techniques produce are sometimes called “builds,” “parts,” “objects,” and “solid imaging products,” which can be formed as a variety of shapes and sizes.
The builds are usually prepared on surfaces referred to as “build pads” or “build platforms,” which can be raised or lowered to place the surface of a build into contact with the actinic radiation and the “working surface” or “build plane” or “image plane” where the build material is exposed.
Despite the variety of devices and methods developed for solid imaging, a number of drawbacks have yet to be resolved in order to make the process more efficient and less costly. This includes for example, improving the otherwise complex and tedious alignment steps for aligning the radiation source and the image plane so that the object is properly formed.